Ambient compensated solar sensor

ABSTRACT

A sensor of solar radiation comprises a pair of matched temperature sensors in fixed thermally insulated relation one to another, one of the pair being exposed to solar radiation and the other shielded from solar radiation.

A United States Patent 1 Day [ AMBIENT COMPENSATED SOLAR SENSOR [75]Inventor: Donald W. Day, Harlem,

Winnebago County, 111.

[73] Assignee: Barber-Colman Company,

Rockford, Ill.

[22] Filed: May 15, 1972 [21] Appl. No.2 253,413

[52] 11.8. CI. 338/25, 73/362 AR, 236/91 [51] Int. Cl 1101c 7/00 [58]Field of Search 338/7, 9,24, 25;

73/339 C, 355 R, 362 AR, 342, 170 R; 236/91; 340/227, 233, 285; 250/833H [56] References Cited UNITED STATES PATENTS 3,619,614 11/1971 Yamaka250/833 H 1 Oct. 23, 1973 Tribus et al 338/25 X Clifford 73/355 XPrimary Examiner-C. L. Albritton Attorney-A. Richard Koch [57] ABSTRACTA sensor of solar radiation comprises a pair of matched temperaturesensors in fixed thermally insulated relation one to another, one of thepair being exposed to solar radiation and the other shielded from solarradiation.

9 Claims, 2 Drawing Figures 1i AMBIENT COMPENSATED SOLAR SENSORBACKGROUND OF THE INVENTION This invention relates to solar thermalradiation sensors for use in automatic temperature regulation.

In a building having a central heating and cooling system, the amount ofheating or cooling required to maintain a constant predeterminedtemperature in different peripheral zones varies with the position ofthe sun and the intensity of the solar radiation. For many years thesolar radiation received by a sensor located to detect the radiationaffecting predetermined zones has been usedto modify the amount ofheating or cooling delivered to such zones. In many installations solarradiation was measured without compensation for ambient temperature.Such installations were unsatisfactory. Other installations used twoseparate sensors one exposed to solar radiation and one shielded fromit. Such installations were also unsatisfactory, because the sensors hadto be separately mounted, had different characteristics and presenteddifficult problems in calibration.

SUMMARY OF THE INVENTION According to this invention the sensors aremounted at the same time, have matching characteristics and require nocalibration. The assembly is simple and inexpensive.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of the ambientcompensated solar sensor partially in section.

FIG. 2 is a schematic circuit showing how the ambient compensated solarsensor may be connected into an external bridge circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT matched thermal sensors, such asresistances, 12, 13-

connected through insulated leads l4, 15, 16, 17 as adjacent arms of thebridge 11, the output from which varies in accordance with relativechanges in temperature of the resistances. The solar sensitiveresistance 12 is embedded as by a thermally conductive potting compound18in a transparent enclosure 19. The enclosure is preferrablycylindrical and closed at one end with the resistance 12 located on theaxis of the cylinder so that the path of solar rays through theenclosure 19 and potting compound 18 to resistance 12 is constant as thesun moves around the axis. The cylindrical shape also tends to focus thesuns rays on the resistance 12. The potting compound is preferrablyblack to absorb the heat. The ambient compensating resistance 13 issimilarly embedded by potting compound 20 in a similar enclosure 21. Theenclosures 19, 21 are mounted in fixed spaced relation on respectiveopposite ends 22, 23 of a tubular insulating pipe or conduit 24 ofsufficient length to prevent heat transfer between the resistances 12,13. Another pipe or conduit 25 is joined perpendicularly to the midpointof insulating conduit 24 to form a tee 26, the ends 22, 23 providing thecrossbar 24 and the perpendicular conduit 25, terminating in a pipefitting 27 or other mounting means, serving as the sole support of thecompensated sensor 10. The leads 14, 15 from solar resistance 12 passthrough end 22 and I support 25 to bridge 1 1. Leads 16, 17 from ambientresistance 13 pass through end 23 and support 25 to the bridge 11. Theleads 14, 15, 16, 17 are all therefore of substantially the same lengthand resistance. An opaque shield, shown as a cup 28 closely fittingaround enclosure 21 and a coating 29 between the cup 28 and end 23,protects the ambient resistance 13 from solar radiation. The shield ispreferably also reflective and resistant to atmospheric corrosion.

Both sensors 12, 13 are subjected to substantially the same ambienttemperature, and, being matched in characteristics, produce the sameresistance in the absence of radiant energy from the sun regardless ofambient temperature. When solar energy is present, it passes through thetransparent enclosure 19 and is absorbed by potting compound 18 to raisethe temperature of solar sensor 12, while it is reflected by the cup 28and so prevented from raising the temperature measured by ambient sensor13. Since the resistances of the sensors 12 and 13 depend upon thetemperatures of the sensors, the resistances will be different. Becauseof the different resistances in the arms of bridge 11, the output of thebridge will be changed to reposition the valve or damper.

While the sensors 12, 13 have been described as thermal sensitiveresistances, they could be thermal current generators or otherthermoelectrical transducers. Although the enclosures 19, 21 and tee 26are preferably madeof plastic that may be easily cemented together,other materials such-as glass and fibre may also be employed.

I claim 1. An ambient compensated solar sensor comprising a support, apair of matched thermal sensors mounted on said support in fixed widelyspaced thermally insulated relation to substantially prevent heattransfer between said thermal sensors, and a shield surrounding andprotecting from solar radiation one of the matched thermal sensors, theother of said matched thermal sensors being unshielded.

2. A solar sensor according to claim 1 additionally comprisingtransparent enclosures for each of said thermal sensors, said enclosuresbeing substantially identical. I

3. A solar sensor according to claim 2 wherein a thermally conductivepotting compound embeds said thermal sensors within the respectiveenclosures.

4. A solar sensor according to claim 1 further comprising an insulatingmember, said thermal sensors mounted on opposite ends of said insulatingmember, and said support joined to the insulating member.

5. A solar sensor according to claim 4 wherein said insulating memberand said support form a tee.

6. A solar sensor according to claim 5 wherein said tee is made ofplastics.

7. A solar sensor according to claim 5 wherein said tee comprisestubular construction.

8. A solar sensor according to claim 7 additionally comprising leadsconnected to the respective thermal sensors and passing through said teefor connection to an external circuit.

9. A solar sensor according to claim 1 wherein said thermal sensors arethermal sensitive resistances.

1. An ambient compensated solar sensor comprising a support, a pair ofmatched thermal sensors mounted on said support in fixed widely spacedthermally insulated relation to substantially prevent heat transferbetween said thermal sensors, and a shield surrounding and protectingfrom solar radiation one of the matched thermal sensors, the other ofsaid matched thermal sensors being unshielded.
 2. A solar sensoraccording to claim 1 additionally comprising transparent enclosures foreach of said thermal sensors, said enclosures being substantiallyidentical.
 3. A solar sensor according to claim 2 wherein a thermallyconductive potting compound embeds said thermal sensors within therespective enclosures.
 4. A solar sensor according to claim 1 furthercomprising an insulating member, said thermal sensors mounted onopposite ends of said insulating member, and said support joined to theinsulating member.
 5. A solar sensor according to claim 4 wherein saidinsulating member and said support form a tee.
 6. A solar sensoraccording to claim 5 wherein said tee is made of plastics.
 7. A solarsensor according to claim 5 wherein said tee comprises tubularconstruction.
 8. A solar sensor according to claim 7 additionallycomprising leads connected to the respective thermal sensors and passingthrough said tee for connection to an external circuit.
 9. A solarsensor according to claim 1 wherein said thermal sensors are thermalsensitive resistances.